Pronunciation: (mez'ärk, mes'-, mē'zärk, -särk), [key]
1. Bot.(of a primary xylem or root) developing from both the periphery and the center; having the older cells surrounded by the younger cells.
2. Ecol.(of a sere) originating in a mesic habitat.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.